Chemistry Paper 1

Question 1

After 1 minute the mean mass = 0.60 
After 2 minutes the mean mass = 1.20 
After 4 minutes the mean mass = 2.40 
After 5 minutes the mean mass = 3.06 
Determine the mean mass of copper produced after 3 minutes

Answer 1

1.80 mg

Question 2

This question is about electrolysis. A student investigates the mass of copper produced during electrolysis of copper chloride solution. Which gas is produced at the positive electrode (anode)?

Answer 2

Chlorine gas

Question 3

This question is about electrolysis. A student investigates the mass of copper produced during electrolysis of copper chloride solution. Copper is produced at the negative electrode (cathode). What does this tell you about the reactivity of copper?

Answer 3

Copper is less reactive than hydrogen

Question 4

Experiment 1 = 3.02 mg 
Experiment 2 = X
Experiment 3 = 3.01 mg 
Mean of all three experiments = 3.06 mg 
Calculate the mass X of copper produced in experiment 2 after 5 minutes

Answer 4

3. 01 + 3.02 + x / 3 = 3.06
4. 06 x 3 = 9.18
5. 18 - 3.01 = 6.17
6. 17 - 3.02 = 3.15
7. 15 mg

Question 5

The copper chloride solution used in the investigation contained 300 grams per dm^3 of solid CuCl2 dissolved in 1dm^3 of water. The student used 50cm^3 of copper chloride solution in each experiment. Calculate the mass of solid copper chloride used in each experiment

Answer 5

50 / 1000 = 0.05
0.05 x 300 = 15
15 g

Question 6

State one similarity and one difference in the electronic structure of sodium and chlorine

Answer 6

Similarity - Both have three levels. Both have incomplete outer shells.
Difference - Sodium has one outer electron shell whereas chlorine has seven. The number of electrons are both different.

Question 7

Sodium atoms react with chlorine atoms to produce sodium chloride (NaCl). Describe what happens when a sodium atom reacts with a chlorine atom. Write about electron transfer in your answer.

Answer 7

Sodium atom loses one electron from its outer shell whereas a chlorine atom gains an electron on its outer shell. Oxidation is loss of electrons but gain of oxygen and reduction is gain of electrons but loss of oxygen.

Question 8

A student plans a method to prepare pure crystals of copper sulphate. The student’s method is: 1. Add one spatula of calcium carbonate to dilute hydrochloric acid in a beaker. 2. When the fizzing stops, heat the solution with a bunsen burner until all the liquid is gone. The method contains several errors and does not produce copper sulphate crystals. Explain the improvements the student should make to the method so that pure crystals of copper sulphate are produced.

Answer 8

1. The dilute hydrochloric acid should be warmed before calcium carbonate is added into a beaker. Use a pipette to add calcium carbonate to the acid solution to increase levels of accuracy.
2. Keep adding calcium carbonate to the acid solution until it no longer reacts.
3. Filter the excess calcium carbonate to leave a solution of salt.
4. Gently warm the salt solution over a bunsen burner so that the water evaporates and crystals of salt are formed.
   Hazards/risks:
   - corrosive acid can cause damage to eyes so eye protection must be worn
   - hot equipment can cause burns so care must be taken when the salt solution is warmed.

Question 9

What is the total number of electrons in a fluorine molecule (F2)?

Answer 9

18 electrons

Question 10

Aluminium reacts with bromine to produce aluminium bromide. Complete the balanced chemical equation for this reaction.

Answer 10

2Al + 3Br2 –> 2AlBr3

Question 11

Explain why diamond has a high melting point

Answer 11

Diamond has a high melting point because it is made up of a strong, rigid covalent lattice. Each carbon atom forms four strong covalent bonds with other carbon atoms. All strong covalent bonds mean that it is a very hard substance with both high melting and boiling points. There are no charged particles so it does not conduct electricity. The bonds forming diamond must be broken for the substance to melt or boil.

Question 12

The relative formula mass pf a group 2 metal carbonate is 197
Relative atomic masses: C = 12 O = 16
Calculate the relative atomic masses of the group 2 metal in the metal carbonate

Answer 12

3 x 16 = 48
48 + 12 = 60
197 - 60 = 137
137

Question 13

A - colourless solution, no solid - pH 14
B - colourless solution, no solid - pH 3
C - colourless solution, solid remains - pH 9
D - colourless liquid, solid remains - pH 7
Identify the solids A, B, C and D. Explain your answers.

Answer 13

A - sodium oxide - because it has highest pH
B - phosphorus oxide - because it has lowest pH
C - magnesium oxide - because it has 2nd highest pH
D - silicon dioxide - because it is neutral

Question 14

10cm^3 = 3
1000cm^3 = X
Calculate the value of X

Answer 14

dilution by a factor of 100

(pH=) 5

Question 15

Iron reacts with dilute hydrochloric acid to produce iron chloride solution and one other product. Name the other product.

Answer 15

Hydrogen

Question 16

Iron reacts with dilute hydrochloric acid to produce iron chloride solution and one other product. Suggest why any unreacted iron can be separated from the mixture.

Answer 16

Due to filtration.

Question 17

Mganesium reacts with iron chloride solution. 3Mg + 2FeCl3 –> 2Fe + 3MgCl2. 0.120g of magnesium reacts with excess iron chloride solution. Relative atomic masses: Mg = 24 Fe = 56. Calculate the mass of iron produced in mg

Answer 17

0.12 / 24 = 0.005
0.005 x 2/3 = 0.00333
0.00333 x 56 = 0.1866 g
187 mg

Question 18

Explain which species is reduced in the reaction between magnesium and iron chloride. Your answer should include the half equation for reduction.

Answer 18

Fe3+ + 3e(-) –>

This is due to the fact reduction is gain of electrons but loss of oxygen.

Question 19

Figure one shows what happens when calcium, copper, magnesium and zinc are added to hydrochloric acid. What is the order of decreasing reactivity of these four metals?

Answer 19

Ca Mg Zn Cn

Question 20

Figure one shows what happens when calcium, copper, magnesium and zinc are added to hydrochloric acid. Name two variables that must be kept constant.

Answer 20

• mass of metal / element
• surface area of metal /element
• concentration of acid
• volume of acid
• temperature of acid

Question 21

Figure one shows what happens when calcium, copper, magnesium and zinc are added to hydrochloric acid. What is the independent variable in this reaction?

Answer 21

type of metal / element

Question 22

Predict the reactivity of beryllium compared with magnesium.

Give a reason for your answer. Use the periodic table.

Answer 22

Beryllium is less reactive.
• greater attraction between nucleus and outer electrons
• more energy is needed to remove electrons
• loss of electrons is more difficult
• outer electrons closer to nucleus
• less shielding

Question 23

A solution of hydrochloric acid contains 3.2 g of hydrogen chloride in 50 cm3. Calculate the concentration of hydrogen chloride in g per dm3

Answer 23

50 / 1000 = 0.05
3.2 / 0.05 = 64
64 g per dm3

Question 24

Give the state symbol for ammonium nitrate solution.

Answer 24

(aq) - aqueous

Question 25

What is the formula of nitric acid?

Answer 25

HNO3

Question 26

Ammonia gas dissolves in water to produce ammonia solution. Ammonia solution contains hydroxide ions, OH–. A student adds a universal indicator to solutions of nitric acid and ammonia. What colour is observed in each solution?

Answer 26

Colour in nitric acid: red | Colour in ammonia solution: purple or blue

Question 27

The student gradually added nitric acid to ammonia solution. Which row, A, B, C or D, shows the change in pH as the nitric acid is added until in excess? A = 10, 7 B = 2, 10 C = 7, 1 D = 10, 2

Answer 27

D = 10, 2

Question 28

Calculate the percentage by mass of oxygen in ammonium nitrate (NH4NO3). Relative atomic masses (Ar): H = 1 N = 14 O = 16 Relative formula mass (Mr): NH4NO3 = 80

Answer 28

3 x 16 = 48 48 / 80 x 100 = 60 60 %

Question 29

Describe a method to investigate how the temperature changes when different masses of ammonium nitrate are dissolved in water. You do not need to write about safety precautions.

Answer 29

``` Method: • use a suitable container eg test tube • use insulation • add water • measure the initial water temperature (with a thermometer) • add stated mass eg 1g or 1 spatula • stir (to dissolve the solid) • measure the final (allow lowest or highest) temperature of the solution • calculate the temperature difference or determine graphically • repeat with different masses • repeat with the same volume of water ```

Question 30

The equation shows the decomposition of hydrogen peroxide. 2 H–O–O–H → 2 H–O–H + O=O Bond: O–O O=O O–H Bond dissociation energy in kJ per mole: 138 496 463 Calculate the overall energy change for the reaction.

Answer 30

``` 4 x 463 = 1852 2 x 138 = 276 1852 + 276 = 2128 4 x 463 = 1852 + 496 = 2348 2128 - 2348 = -220 ```

Question 31

What order did scientists use to arrange elements in early periodic tables?

Answer 31

atomic weight

Question 32

In the early periodic tables some elements were placed in the wrong groups. Mendeleev overcame this in his periodic table. Give one way Mendeleev did this.

Answer 32

left gaps / spaces and changed the order based on atomic weights

Question 33

``` Element Boiling point in °C Fluorine –186 Chlorine –34 Bromine +59 Explain why the boiling points in Table 2 are low. ```

Answer 33

Weak intermolecular forces so little energy required to overcome / break the forces between molecules.

Question 34

Explain the trend in the boiling points in Table 2.

Answer 34

The molecules get larger going down the group so the intermolecular forces increase so the boiling points increase with increasing relative atomic mass.

Question 35

Explain why neon is unreactive. Give the electronic structure of neon in your answer.

Answer 35

2,8 so stable arrangement of electrons

Question 36

How many atoms are there in 1 g of argon? The Avogadro constant is 6.02 × 1023 per mole. Relative atomic mass (Ar): Ar = 40

Answer 36

0. 025 x 6.02 x 10^23 | 1. 51 x 10^22

Question 37

Some metals are extracted from molten compounds using electrolysis. Why is electrolysis used to extract some metals?

Answer 37

Metal is too reactive to be extracted using carbon as it would react with carbon

Question 38

Aluminium is produced by electrolysis of a molten mixture. What two substances does the molten mixture contain?

Answer 38

Aluminium oxide and cryolite

Question 39

Copper and chlorine are produced when molten copper chloride is electrolysed. Complete the half equation for the reaction at each electrode.

Answer 39

negative electrode: Cu2+ + 2e– → Cu positive electrode: 2Cl– → Cl2 + 2e–

Question 40

The student: • measured the mass of copper deposited on the negative electrode after 60 minutes • compared the mass deposited with the expected value. Suggest two reasons why the mass deposited was different from the expected value.

Answer 40

* concentration / volume of solution was different * impurities in solution * error in timing * copper falls off electrode * copper removed when drying electrode * electrode not dry when weighed * voltage / current was different

Question 41

Sodium reacts with chlorine. What is the balanced equation for the reaction?

Answer 41

2 Na + Cl2 → 2 NaCl

Question 42

Hot sodium is put in a gas jar of chlorine. Describe the observations made before, during and after the reaction.

Answer 42

Before - silver solid / liquid / metal During - yellow flame After - white solid / powder

Question 43

Explain why sodium is less reactive than potassium.

Answer 43

sodium has fewer energy levels / shells making it less reactive because the outer electron / shell is closer to nucleus due to the strong attractive force and so the outer electron is less easily lost.

Question 44

Chlorine reacts with sodium and with hydrogen. Compare the structure and bonding in sodium chloride and hydrogen chloride.

Answer 44

sodium chloride hydrogen chloride differences in bonding - ionic covalent metal & non-metal two non-metals transferring electrons sharing electrons ions (Na+ and Cl – ) molecules charged particles neutral or no overall charge differences in structure - giant structure or lattice small / simple / discrete molecules electrostatic intermolecular forces (electrostatic forces) are strong (intermolecular forces) are weak act in all directions random or between the molecules regular irregular / random similarities in bonding- full shells or stability full shells or stability (transferring) electrons (sharing) electrons, strong bonds strong (covalent) bonds similarities in structure - (electrostatic) forces (intermolecular) forces

Question 45

An aluminium atom is represented as: Al 13 27 Give the number of electrons and neutrons in the aluminium atom.

Answer 45

Number of electrons - 13 | Number of neutrons - 14

Question 46

Aluminium is produced by the reduction of aluminium oxide (Al2O3). What is meant by the term reduction?

Answer 46

Loss of oxygen

Question 47

Oxygen is formed at the positive carbon electrodes. Explain why the positive carbon electrodes must be continually replaced.

Answer 47

At high temperature oxygen reacts with carbon so the positive electrode wears away to produce carbon dioxide.

Question 48

A substance conducts electricity because of free moving, charged particles. What are the free moving, charged particles in a: • carbon electrode (made from graphite) • molten mixture of aluminium oxide and cryolite • metal wire?

Answer 48

Carbon electrode: delocalised electrons Molten mixture of aluminium oxide and cryolite: ions Metal wire: delocalised electrons

Question 49

Suggest one limitation of using a ball and stick model for a water molecule.

Answer 49

* not to scale * not 3 dimensional * incorrect arrangement in space * electrons and shells not shown

Question 50

Ice has a low melting point. Water molecules in ice are held together by intermolecular forces. Complete the sentence.

Answer 50

Ice has a low melting point because the intermolecular forces are weak.

Question 51

What is the number of bonds formed by each carbon atom in diamond?

Answer 51

4

Question 52

Give two physical properties of diamond.

Answer 52

* very hard * very high melting point * does not conduct electricity

Question 53

Name two other substances with giant covalent structures.

Answer 53

graphite and silicon dioxide

Question 54

Plan a method the students could use to test their hypothesis. You should show how the students use their results to test the hypothesis. You do not need to write about safety precautions.

Answer 54

* weigh test tube * add metal carbonate * weigh test tube and metal carbonate * heat * allow to cool * weigh test tube and metal oxide * repeat (heat, cool and weigh) until no change in mass * determine mass of metal carbonate used * determine mass of carbon dioxide produced * repeat with different metal carbonate